Many computers have plug-in bus architectures, with a motherboard or other backplane having multiple bus slots. Each slot accommodates a single printed circuit board (PCB), with a bus controller circuit on the board to transmit and receive communications over the bus. Recently, Intel® introduced processors with interfaces to the PCI Express (PCIe®) bus that are capable of “PCIe slot bifurcation,” meaning that different groups of bus lanes can be operated separately by different controllers. In this regard, for example, U.S. Patent Application Publication 2012/0260015 describes a PCIe port bifurcation card that includes a PCIe interface and a plurality of PCIe devices, each independently coupled to the interface via an unswitched connection. In most systems, however, each plug-in card is limited to a single bus interface.
Some plug-in cards are capable of connecting to multiple bus slots. For example, U.S. Pat. No. 5,572,688 describes a computer that has a primary bus including a primary bus interconnection slot and a secondary bus including a secondary bus interconnection slot. A primary bus card has a primary bus connector region for connection with the primary bus interconnection slot. The primary bus card includes a processing circuit electrically connected to the primary bus connector region to process primary bus signals from the primary bus. In addition, the primary bus card has a bridge cable connector electrically connected to the processing circuit. A secondary bus connector is positionable within the secondary bus interconnection slot. A bridge cable is connected between the bridge cable connector and the secondary bus connector to convey secondary bus signals from the secondary bus connector to the processing circuit.
As another example, U.S. Pat. No. 5,740,378 describes a communication system having an over-the-top ribbon cable data bus configuration. The ribbon cables are segmented and redirected between individual circuit boards and a backplane data bus. Each ribbon cable connects either directly to the backplane or to an interposer board coupled between the circuit board and the backplane.